1. Field of the Invention
This invention relates to a process for producing fuels. More specifically, the invention relates to an energy efficient process of producing jet fuels utilizing biological fatty acid sources.
2. Background of the Invention
Alkyl esters, including methyl ester or ethyl ester, also known as “biodiesel”, are a renewable and clean burning alternative to conventional petroleum-derived diesel fuel. Biodiesel is made from a raw or used vegetable oil or animal fat, typically soybean oil or rapeseed oil (which are composed of triglycerides, diglycerides, monoglycerides, fatty acids (FA), or combinations thereof). Because biodiesel is made from natural oil or fat sources, the alkyl esters typically comprise C14 to C18 fatty chains if derived from vegetable oil, and C16 to C22 fatty chains if derived from animal fat. Biodiesel can be combusted in diesel (combustion-ignition) engines either in pure form or as blended with petroleum-derived diesel fuel. Biodiesel provides the benefits of a renewable resource as well as providing lower sulfur emissions than petroleum diesel.
A common route to produce biodiesel from biologically derived oils is through a process called transesterification. A common transesterification process is illustrated below.
However, biodiesel produced by this process typically does not meet transportation diesel requirements, e.g., these esters typically gel below −10° C. For improved performance, thermal and catalytic chemical bond-breaking (cracking) technologies have been developed that enable converting bio-oils into bio-based alternatives to petroleum-derived diesel fuel and other fuels, such as jet fuel.
Cleaving FA chains from glycerol and cracking longer FA chains into shorter (lower-carbon-number) molecules are used to ensure adequate fuel flow performance at low (down to −50° C.) temperatures, oxygen removal is required to ensure adequate fuel energy density, and replacement of oxygen with hydrogen is required to ensure fuel chemical stability (resistance to polymerization). Because additional energy input is required to crack C16 and C18 FA chains (which comprise the primary FA constituents of soybean, sunflower, corn, rapeseed, canola, cottonseed, and other common vegetable oils) into shorter molecules, the overall energy efficiency of such a process is diminished.
Consequently, there is a need for a more energy efficient method of producing fuels from biological sources such as natural oils and fats.